1. Field of the Invention
The present invention relates to a paste application apparatus which applies a paste, for example, an adhesive, conductive adhesive, external electrode, or flux, to a target for coating, for example, an electronic component, and a method for applying a paste.
2. Description of the Related Art
An example of the aforementioned type of paste application apparatus is disclosed in Japanese Unexamined Patent Application Publication No. 10-41339. As shown in FIG. 8, this is provided with a coating applicator (roller) 2 for circulating and moving a paste 3 in a constant direction in order that the circumferential velocity V2 at the coating area A becomes a constant, a storage portion 1 for storing the paste 3 and bringing this paste into contact with the coating applicator 2, a squeegee 4 for adjusting the liquid thickness of the paste on the coating applicator in order that the thickness, that is, layer thickness, of the paste on the coating applicator 2 becomes constant in the coating area A, and a head 5 for moving the target for coating in the horizontal direction to a position 11, in order that when the target for coating 6 crosses the coating area A, the movement velocity V1 of the target for coating and the circumferential velocity V2 become in agreement with each other.
Another apparatus of this type is disclosed in Japanese Patent No. 3131156 (Japanese Unexamined Patent Application Publication No. 6-296929). Regarding this apparatus, as shown in FIG. 9, a predetermined quantity of paste 3 is adhered to the perimeter of a rotating thin disk-shaped coating disk 7, the paste adhered to the perimeter of the aforementioned coating disk 7 is transferred to the side surface of the chip-shaped components c while the chip-shaped components c as targets for coating are moved linearly in the tangential direction of the aforementioned disk 7 and, in addition, the shape of the paste e applied to each chip-shaped component c can be appropriately changed by controlling the difference between the circumferential velocity V2 of the perimeter of the aforementioned coating disk 7 and the movement velocity V1 of the chip-shaped component c during this transfer.
Another known paste application apparatus is shown in FIGS. 24A and 24B. A coating roller 103 having a width corresponding to the coating width is immersed in a paste bath 101 storing a paste 102 and is rotated so as to form a paste layer 102a having a predetermined thickness on the perimeter of the coating roller 103, and a target for coating 106 is brought into contact with this paste layer 102a so as to transfer and apply the paste. Specifically, a paste application apparatus for applying the paste to one surface of the target for coating, for example, an electronic component, is disclosed in Japanese Unexamined Patent Application Publication No. 10-41339.
This paste application apparatus is provided with a roller which is supplied with the paste to the perimeter surface and which rotates in one direction, and a transport mechanism which transports the target for coating in the condition that one surface thereof faces toward the perimeter surface of the roller to a required position above this roller, and the paste is applied to the one surface of the target for coating via the roller. In this paste application apparatus, the coating thickness of the paste with respect to one surface of the target for coating is determined by the adherence thickness of the paste with respect to the perimeter surface of the roller.
Furthermore, in this paste application apparatus, the paste is supplied to the perimeter surface of the roller rotating in one direction. The target for coating is transported to the required position above the roller in the condition that one surface thereof faces toward the perimeter surface of the roller. According to this, the paste is applied to the target for coating via the roller.
Specifically, this paste application apparatus is as shown at 411 in FIG. 53, and is provided with a cylindrical roller 412, a paste storage portion 419 for storing the paste, a movement mechanism 416 for moving the targets for coating 417 in order to bring them into contact with the paste layer 414 on the roller, and a squeegee 415 for adjusting the paste adhered to the perimeter of the roller 412 to have a constant film thickness.
In this paste application apparatus 411, when the roller 412 is rotated, the paste stored in the paste storage portion 419 is adhered to the perimeter of the roller 412. The paste adhered to the perimeter of the roller is adjusted to have a predetermined thickness by the squeegee 415 and, therefore, the paste layer 414 is produced. On the other hand, the movement mechanism 416 is for horizontally moving the adsorbed target for coating 417 above the roller 412 at the height at which the target for coating 417 is partially immersed in the paste layer 414 and, therefore, the paste is applied to the target for coating 417 when the bottom surface of the target for coating 417 passes through the paste layer.
Other conventional paste application apparatus is disclosed in Japanese Unexamined Patent Application Publication No. 8-19752. In this paste application apparatus, a paste is applied to the target for coating via a horizontal disk-shaped base. The paste is supplied along an arc-shaped path on the base with a predetermined thickness. The target for coating is pressed against the paste on the base.
The paste applied as described above is applied to the top surface portion or bottom surface portion, and the front portion and rear portion in the chip type electronic component, and it is desirable that the front portion and the rear portion are coated evenly. That is, for example, when the paste is a conductive adhesive, in mounting the electronic component, which is the target for coating after being coated, on a circuit substrate, occurrence of failure in mounting can be reduced by evenly joining the front and rear portion of the electrode of the component to the wiring of the substrate.
Among the aforementioned conventional techniques, regarding the former application apparatus, the coating applicator, for example, a roller, has an arc-shaped perimeter surface. When the paste is applied to the target for coating by horizontal movement of the head during movement of the paste layer together with the rotation of the roller, the target for coating has components of movement in both of the vertical and horizontal directions relative to the paste surface in the coating area (in the paste). Then, the target for coating scrapes the paste by the quantity of movement in the horizontal direction among them. Even when the paste layer surface of the coating applicator moves at a velocity equivalent to the movement velocity of the target for coating, difference in this component of movement in the horizontal direction (quantity of horizontal movement) occurs between the front portion and the rear portion of the target for coating. Consequently, difference in the quantity of scraping of the paste occurs between the front portion and the rear portion of the target for coating due to this difference in the quantity of horizontal movement and, therefore, difference in the quantity of coating occurs.
The reason for this will be described with reference to FIG. 5. This FIG. 5 shows orthogonal coordinates of the coordinate system viewed from the side with respect to the movement direction of the target for coating centering the hypothetical reference point O that is an arbitrary point on the paste layer surface moving together with the rotation of the roller. Here, the horizontal axis is the tangent to the paste layer surface at the point of contact of the hypothetical reference point O, and the vertical axis is the direction perpendicular to the tangent (the direction of the normal to the paste layer surface) passing through the hypothetical reference point O. Regarding the abscissa, the movement direction of the target for coating is indicated by plus, and regarding the ordinate, the direction of moving away from the paste layer surface is indicated by plus. The target for coating is assumed to be a rectangular parallelepiped. FIG. 5 shows the process of immersion of the rectangular parallelepiped target for coating in the paste layer as relative movement trajectories a2 and b2 of the front lower end position and rear lower end position, respectively, of the target for coating relative to the aforementioned hypothetical reference point O. That is, when the hypothetical reference point O moving practically at a constant velocity in the same manner as the paste layer surface is assumed to be fixed at the center of the coordinates, the movement trajectories a2 and b2 shown in this FIG. 5 indicate relative positional relationship between the hypothetical reference point O and the aforementioned front lower end position and rear lower end position. Here, the hypothetical reference point O is set to pass through the center position of the width from the front to the rear of the target for coating in the movement direction as well as the aforementioned normal when the target for coating being immersed in the paste layer reaches the deepest point. The horizontal component of the velocity among the movement velocity of the paste layer surface is set to agree the horizontal movement velocity of the target for coating at the uppermost position in the arc-shaped movement path.
In this case, when the hypothetical reference point O is in the neighborhood of the uppermost position, the movement velocity of the target for coating is larger than the horizontal component of the velocity among the components of the movement velocity of the paste layer surface. Consequently, since the movement velocity of the front portion of the target for coating was relatively larger than the movement velocity of the paste layer between the start of immersion and the completion of immersion, the quantity L1 of relatively forward horizontal movement of the front portion of the target for coating relative to the paste layer was larger than the quantity L2 of relatively backward horizontal movement of the rear portion of the target for coating relative to the paste layer.
Therefore, regarding this conventional technique, the paste extrusion quantity of the front portion of the target for coating is increased. Conversely, the paste extrusion quantity of the rear portion of the target for coating is decreased. According to this, the paste application quantity of the front portion of the target for coating became larger than that of the rear portion and, therefore, the requirement for even application quantities of the front portion and the rear portion was not met. Consequently, in order to evenly apply the paste to the front portion and the rear portion of the target for coating, after the target for coating was coated, the horizontal orientation was reversed and the coating operation had to be performed again and, therefore, there was a problem of low efficiency in operation.
Regarding the paste application apparatus shown in FIG. 9, the movement velocity V2 of the paste surface of the disk 7 for applying paste is made larger than the movement velocity V1 of the target for coating for the purpose of intensively adhering the paste e to the rear portion of the target for coating c, and even application of the paste to the front portion and the rear portion of the target for coating c was not intended.
Regarding the conventional paste application apparatus shown in FIGS. 24A and 24B, since the coating roller 103 having a width corresponding to the coating width was used, when the coating width was changed, an extensive coating roller exchange operation including release from a rotation drive mechanism, disassembling of a bearing portion, etc., had to be performed, a great deal of manpower and time was required for preparation and exchange thereof. In particular, regarding a small coating width, as shown in FIG. 24B, the coating roller 103 became a thin disk-shaped one, the stiffness of the coating roller itself became low and, therefore, there were problems in that runouts and deformation of the coating roller 103 were likely to occur, and variations in the application positions and coating dimensions occurred. When such a disk-shaped coating roller 103 is used, since the stiffness of the coating roller itself is low, adjustment of the thickness of the paste layer formed on the roller perimeter by a squeegee, etc., is difficult. Consequently, a method in which the coating roller 103 is immersed in a paste bath and is rotated so as to transfer and apply to the target for coating with the shape as is adhered to the roller perimeter is adopted. However, as shown in the drawing under magnification in FIG. 24B, regarding the paste layer 102a adhered to the roller perimeter, the thickness and the shape of the coating width of the side surface were not stabilized, the dimensions of the paste transferred and applied to the target for coating were likely to vary and, therefore, it was difficult to perform coating with high precision.
In the conventionally known apparatus as disclosed in Japanese Unexamined Patent Application Publication No. 2001-53086, a paste is applied individually to a pair of fixed inclined surfaces which are inclined in order to increase the distance therebetween in an upward direction, and the target for coating is positioned above the pair of inclined surfaces. Subsequently, the target for coating is allowed to move down, edge portions composed of the bottom surface and side surface of both end portions of the target for coating are brought into contact with respective corresponding inclined surfaces and, therefore, the paste is applied to the bottom surface and side surface of both end portions of the target for coating.
However, regarding this conventional configuration, since operations of horizontal movement or termination of the head for holding and moving this target for coating and operations of vertical movement of the head, etc., are required in order to apply the paste to all over the target for coating, the operation of paste application cannot be performed rapidly and, therefore, there was a problem in that production efficiency was low.
Targets for coating may be required to coat not only one surface, but also the other surfaces. For example, piezoelectric vibration components must be fixed firmly to a substrate in order to prevent excessive vibration thereof. Consequently, large quantities of adhesives must be applied to the piezoelectric vibration components. In such a case, regarding the aforementioned paste application apparatus, the quantity of the paste adhered to the perimeter surface of the roller must be increased so as to increase the thickness of adherence.
In this case, when the quantity of the paste adhered to the perimeter surface of the roller is increased, the centrifugal force of the paste accompanying the rotation of the roller is increased and, therefore, the paste may be peeled off the perimeter surface of the roller and be fly into the surroundings. In order to prevent such flying of the paste, it is considered to decrease the rotation speed of the roller.
However, when the rotation speed of the roller is decreased, although flying of the paste can be prevented, the application speed of the paste is decreased and, therefore, the operation efficiency is reduced. The contact time of the paste with air is increased and, therefore, degradation of the paste is accelerated. As described above, it is not easy to increase the thickness of adherence of the paste to the perimeter surface of the roller without reduction of the rotation speed of the roller according to the aforementioned paste application apparatus.
On the other hand, an apparatus for applying a paste to a sheet-shaped target for coating by a roller is disclosed in Japanese Unexamined Patent Application Publication No. 9-225369. In this paste application apparatus, many grooves 222 having a narrow groove width are arranged parallel to the axis direction on the perimeter surface of the roller 221 as shown in FIG. 39. The quantity of the paste adhered and held on the perimeter surface of the roller 221 can be increased by the many grooves.
However, regarding such a structure, even if the quantity of the paste held on the perimeter surface of the roller can be increased, the thickness of adherence of the paste with respect to the perimeter surface of the roller cannot be made an adequate thickness. When chip-shaped or block-shaped targets for coating are coated with pastes, the targets for coating are interfered by concave and convex protrusions arranged on the roller perimeter and, therefore, the portions to be coated with the paste of the target for coating cannot be immersed deeply in the paste to the extent that the side surfaces are immersed in the paste.
Regarding the paste application apparatus in the aforementioned Japanese Unexamined Patent Application Publication No. 10-41339 (FIGS. 24A and 24B), since there is no regularity with respect to the position at which the paste to be applied to the target for coating at the application position should be located, the paste being adhered on the perimeter surface of the roller, it may take a long time depending on the position on the perimeter surface of the roller until the paste is applied to the target for coating.
Among the pastes adhered on the perimeter surface of the roller, the paste which has not been applied to the target for coating passes through the paste supply portion again. However, in general, the paste which has ever been adhered to the perimeter surface of the roller is not adequately mixed with other pastes even if after passing through the paste supply portion.
Consequently, in many cases, the paste is adhered on the perimeter surface of the roller for a long time, and the surface layer of the paste is likely to bring about change in viscosity due to contact with the external air. In particular, a high viscosity paste has a remarkable tendency to become unlikely to mix with the paste in the paste supply portion, the viscosity change occurs at an earlier stage. When the viscosity of the paste is changed, the quantity of the paste applied to the target for coating is changed to increase or decrease. According to this, there is a problem in that continuous use of the paste for a long time is difficult.
Furthermore, the paste application apparatus in the aforementioned Japanese Unexamined Patent Application Publication No. 8-19752 is provided with a squeegee for scraping the paste after contact with the target for coating off the base and for dividing and directing the paste toward both sides. The pastes are mixed with each other and are self-agitated at a rearward position of this squeegee. Therefore, the viscosity increase due to drying of the paste can be controlled at a low level.
However, at least tip portion of the aforementioned squeegee is composed of an elastic body like rubber, this tip portion wears and the resulting powders are mixed into the paste and, therefore, the quality of the paste is degraded. Degradation and curing of the paste are accelerated by the frictional heat of the surface to which the paste is adhered and the squeegee and, therefore, the life of the paste is reduced. Furthermore, there are various problems in that, for example, adjustment of position or exchange of the squeegee in which the tip portion wears is required frequently and, therefore, maintenance requires much expense in time and effort.
Regarding the conventional paste application apparatus 411 shown in FIG. 53, when the rotation speed of the roller 412 is increased in order to increase the application speed of the paste, there is a problem in that the temperature of the paste is increased due to the frictional heat generated between the squeegee 415 and the paste during adjustment of the paste film thickness by the squeegee 415. Then, the viscosity of the paste is decreased, and the quantity of the coating becomes unstable. In addition, for example, when the paste is a thermosetting resin, the temperature is increased continuously so as to reaches the curing start temperature and, therefore, the paste is cured so that the paste may not be applied.
The present invention was made in consideration of the aforementioned circumstances. Accordingly, it is an object of the present invention to provide a paste application apparatus and a method for applying a paste, each capable of evenly applying a paste to each of the front portion and the rear portion of a target for coating with a simple operation.
It is a further object of the present invention to provide a paste application apparatus capable of performing application with high precision, performing prompt change of the coating width with ease, and achieving improvement of production efficiency.
It is a further object of the present invention to provide a paste application apparatus capable of applying large quantities of paste to a target for coating while flying of a paste from a roller is prevented.
Furthermore, the present invention is to overcome at least one of the aforementioned various problems in order that a paste can be used continuously for a long time.
It is further object of the present invention to provide a paste application apparatus capable of applying a paste to a target for coating for a long time with stability while the temperature increase of the paste is suppressed and the viscosity of the paste is kept constant even when a roller is rotated at a high speed.
In order to achieve the aforementioned objects, the present invention has following configurations.
A paste application apparatus according to the present invention includes a setting device for setting the velocity difference between the movement velocity of a target for coating and the movement velocity of a paste layer in order to evenly apply a paste to the front portion and the rear portion of the aforementioned target for coating during application of the paste to the aforementioned target for coating, wherein the paste layer having a constant layer thickness is formed on a substrate surface, the aforementioned paste layer moves along a path which is an arc-shaped path when viewed from the side together with the substrate, and the target for coating moves along the tangential direction of the aforementioned arc-shaped path, along which the aforementioned paste layer moves, while the aforementioned target for coating is immersed until a predetermined depth relative to the aforementioned paste layer and thereby the paste is applied to the aforementioned target for coating.
According to the paste application apparatus of the present invention, since the paste is evenly applied to the front portion and the rear portion of the target for coating by setting the velocity difference between the movement velocity of the target for coating during application of the paste and the movement velocity of the paste layer during application of the paste, excellent desired application of the paste can be performed by simple velocity control of only setting the velocity difference.
Preferably, the aforementioned arc-shaped path is set by the perimeter surface of a cylindrical roller, the aforementioned paste layer is adhered to the surface of the aforementioned arc-shaped path and, in addition, a supply portion for supplying the paste to the surface of the aforementioned arc-shaped path and a layer thickness adjustment portion for keeping the layer thickness of the paste layer on the surface of the aforementioned arc-shaped path constant are included. In this case, since the arc-shaped path, along which paste layer moves, is set by the perimeter surface of the cylindrical roller, and when the paste layer moves along the arc-shaped path, the paste is evenly applied to the front portion and the rear portion of the target for coating by setting the velocity difference between the movement velocity of the paste layer and the movement velocity of the target for coating, excellent desired application of the paste can be performed by simple velocity control of only setting the velocity difference.
Preferably, the aforementioned setting device sets the velocity difference between the movement velocity of the aforementioned paste layer and the movement velocity of the aforementioned target for coating during application of the paste at the position of application of the paste to the aforementioned target for coating with the paste based on the distance from the center of the arc of the aforementioned arc-shaped path to the aforementioned paste layer surface, the immersion depth of the aforementioned target for coating in the aforementioned paste layer, and the external dimensions of the aforementioned target for coating. In this case, since the velocity difference between the movement velocity of the paste layer on the arc-shaped path and the movement velocity of the target for coating during application of the paste can be simply set by determination using parameters of the distance from the center of the arc of the arc-shaped path to the paste layer surface, the immersion depth of the target for coating in the paste layer, and the external dimensions of the target for coating, the aforementioned velocity difference can be simply determined only by calculation even when various conditions are changed.
Preferably, the aforementioned substrate is composed of the cylindrical roller driven to rotate and, in addition, a supply portion for supplying the paste to the surface of the aforementioned roller, and a layer thickness adjustment portion for keeping the layer thickness of the paste layer on the surface of the aforementioned roller constant are included. In this case, the paste layer adhered on the roller surface is allowed to be in the condition of being rotated and moved accompanying the rotation of the roller, and when the target for coating is passed and moved along the tangential direction relative to the paste layer rotating and moving, the paste of the paste layer on the roller surface is applied to the target for coating.
Preferably, the aforementioned setting device sets the velocity difference between the movement velocity of the aforementioned paste layer and the movement velocity of the aforementioned target for coating during application of the paste at the position of application of the paste to the aforementioned target for coating based on the distance from the center of the aforementioned roller to the aforementioned paste layer surface, the immersion depth of the aforementioned target for coating in the aforementioned paste layer, and the external dimensions of the aforementioned target for coating. In this case, since the velocity difference between the movement velocity of the paste layer on the arc-shaped path and the movement velocity of the target for coating during application of the paste can be simply set by determination using parameters of the distance from the center of the roller to the paste layer surface, the immersion depth of the target for coating in the paste layer, and the external dimensions of the target for coating, the aforementioned velocity difference can be simply determined only by calculation even when various conditions are changed.
Preferably, the aforementioned setting device sets the movement velocity of the aforementioned paste layer at a velocity higher than the movement velocity of the aforementioned target for coating during application of the paste. In this case, by setting the movement velocity of the paste layer on the arc-shaped path at a velocity higher than the movement velocity of the target for coating during application of the paste, the quantities of application to the front portion and the rear portion of the target for coating can be made even.
Preferably, the aforementioned setting device sets the aforementioned velocity difference in order that regarding respective movement trajectories of immersion of the aforementioned front portion and the aforementioned rear portion in the movement direction of the aforementioned target for coating relative to the aforementioned paste layer during immersion in the aforementioned paste layer, the immersion start position and the immersion completion position become in agreement with each other. In this case, the respective quantities of forward or backward movement of the front portion and the rear portion of the target for coating in the condition of being immersed in the paste layer become the same and, therefore, the quantities of application of the paste on respective surface portions become the same.
A method for applying a paste according to the present invention includes the step of applying a paste to a target for coating by setting the velocity difference between the movement velocity of the aforementioned target for coating during application of the paste and the movement velocity of a paste layer during application of the paste in order to evenly apply the paste to the front portion and the rear portion of the aforementioned target for coating, wherein the paste layer having a constant layer thickness is formed on a substrate surface, the aforementioned paste layer moves along a path which is an arc-shaped path when viewed from the side together with the substrate, and the target for coating moves along the tangential direction of the aforementioned arc-shaped path, along which the aforementioned paste layer moves, while the aforementioned target for coating is immersed until a predetermined depth relative to the aforementioned paste layer and thereby the paste is applied to the aforementioned target for coating.
According to the paste application apparatus of the present invention, since the paste is evenly applied to the front portion and the rear portion of the target for coating by setting the velocity difference between the movement velocity of the target for coating during application of the paste and the movement velocity of the paste layer during application of the paste, excellent desired application of the paste can be performed by simple velocity control of only setting the velocity difference.
Another paste application apparatus according to the present invention is provided with a coating roller for transferring and applying a paste to a target for coating, a device for supplying the paste to the perimeter of the coating roller, and a paste layer formation member for scraping off an excess portion of the paste supplied to the perimeter of the roller and forming a paste layer having a predetermined cross-sectional shape on the perimeter of the coating roller, wherein the shape of the aforementioned paste layer formation member is set to form the paste layer having a width smaller than the width in the axis center direction of the coating roller as the paste layer, the aforementioned target for coating is held by a movable head, the paste is applied to the aforementioned target for coating by immersing the aforementioned target for coating in the aforementioned paste layer while the aforementioned head moves on the aforementioned rotating coating roller, and the aforementioned paste layer formation member is composed of a fixed squeegee provided with a concave portion at the tip portion.
According to this configuration, since the excess portion of the paste supplied to the perimeter of the coating roller is scraped off by the paste layer formation member, the paste layer having a width smaller than the width in the axis center direction of the coating roller can be formed on the perimeter of the coating roller, and by bringing the target for coating into contact with this past layer, the paste can be transferred and applied with a desired width.
In this case, since the width of the coating roller itself is not restricted by the coating width, even when a coating of a small width is performed, a wide coating roller having high stiffness can be used, and inconveniences, for example, runouts and deformation of the coating roller, do not occur.
Since the coating width is determined by the shape of the paste layer formation member, change of the coating width can be performed by exchange of the paste layer formation member only, and exchange of the coating roller is unnecessary.
Since the paste is applied to the target for coating by immersing the target for coating in the paste layer on the coating roller while the target for coating moves on the rotating coating roller, the coating step can be performed in a short time. Consequently, the operation of application of the paste to the target for coating can be efficiently performed and, therefore, the productivity can be improved.
Since an edge for scraping off the paste is set in accordance with the shape and position of the concave portion of the tip portion for scraping off the paste of the plate-shaped squeegee (paste layer formation member), a paste layer having an arbitrary width and thickness can be formed at an arbitrary position of the coating roller perimeter. Consequently, squeegees corresponding to various targets for coating may be prepared in advance, and the fixed squeegee may be exchanged in accordance with change of the target for coating.
The aforementioned paste layer formation member may be composed of a rotary roller provided with a circular concave groove on the perimeter.
According to this configuration, by setting the shape and position of the circular concave groove formed on the perimeter of the rotary roller (paste layer formation member), a paste layer having an arbitrary width and thickness can be formed at an arbitrary position of the coating roller perimeter. Even when the rotary roller is brought into contact with the perimeter of the coating roller and the excess portion of the paste is completely removed from the perimeter of the coating roller, since the coating roller and the rotary roller are only brought into rolling contact with each other, frictional heat and wear do not occur, and even when continuous operation is performed, degradation of the paste due to temperature increase and mixing of powders resulting from wear into the paste can be avoided before they happen.
Preferably, a circular convex thread is arranged on the perimeter of the aforementioned coating roller, and a concave portion to be fitted with this circular convex thread is arranged in the aforementioned paste layer formation member.
According to this configuration, by scraping off the excess portion of the paste supplied to the perimeter of the coating roller with the paste layer formation member, a paste layer having a desired thickness can be formed in the condition of being stable with respect to the shape on the perimeter of the circular convex thread of the coating roller, and by bringing the target for coating close to the coating roller in order to allow the circular convex thread of the coating roller to fit into the concave portion of the target for coating, the paste can be transferred and applied to the bottom of the concave portion of the target for coating with a desired width.
Preferably, the aforementioned paste layer formation member is composed of a fixed squeegee provided with a taper-shaped concave portion at the tip portion.
Here, xe2x80x9cthe concave portion arranged at the tip portion is in the shape of a taperxe2x80x9d refers to that the side edge of the concave portion for scraping off the excess portion of the paste of the paste layer of the coating roller side is an edge inclined relative to the axis center direction of the coating roller and the diameter direction of the coating roller. Consequently, regarding the concave portion, an inclined side surface portion is formed in the paste layer when the excess portion of the paste layer on the coating roller side is scraped off.
According to this configuration, the inclined side surface portion is formed in the paste layer of the coating roller by the fixed squeegee provided with the taper-shaped concave portion, and the target for coating is immersed in the inclined side surface portion of the paste layer so that application of the paste can be performed. Since such an inclined side surface portion of the paste layer is a space portion in which the target for coating is moved in the condition of being held by the head, application of the paste to the target for coating can be performed by a simple operation of only moving the target for coating by the head in order to apply the paste.
Since the paste is applied to the target for coating by immersing the target for coating in the paste layer on the coating roller while the target for coating moves on the rotating coating roller, and movement of the target for coating during application can be performed by moving between a pair of inclined surfaces on the coating roller side along a constant direction, for example, the horizontal direction, the coating step can be performed in a short time. Consequently, the operation of paste application to the target for coating can be efficiently performed and, therefore, the productivity can be improved.
Preferably, the aforementioned paste layer formation member is composed of a rotary roller provided with a taper-shaped circular concave groove on the tip portion.
Here, xe2x80x9cthe circular concave groove arranged at the tip portion of the rotary roller is in the shape of a taperxe2x80x9d refers to that the side surface of the circular concave groove for scraping off the excess portion of the paste layer of the coating roller side is a surface inclined relative to the axis center direction of the coating roller and the diameter direction of the coating roller. Consequently, regarding the circular concave groove, an inclined side surface portion is formed in the paste layer when the excess portion of the paste layer on the coating roller side is scraped off.
According to this configuration, the inclined side surface portion is formed in the paste layer on the coating roller by the rotary roller provided with the taper-shaped circular concave groove, and application of the paste can be performed by immersing the target for coating in the inclined side surface portion of the paste layer. Consequently, since such an inclined side surface portion of the paste layer is a space portion in which the target for coating is moved in the condition of being held by the head, application of the paste to the target for coating can be performed by a simple operation of only moving the target for coating by the head in order to apply the paste.
Preferably, a coating roller for transferring and applying a paste to a target for coating, a device for supplying the paste to the perimeter of the coating roller, and a paste layer formation member for scraping off an excess portion of the paste supplied to the perimeter of the roller and forming a paste layer having a predetermined cross-sectional shape on the perimeter of the coating roller are arranged and, in addition, taper-shaped circular convex threads are arranged at both edge portions on the aforementioned perimeter of the coating roller, and concave portions to be fitted with these circular convex threads are arranged in the aforementioned paste layer formation member.
Here, xe2x80x9cthe circular convex thread is in the shape of a taperxe2x80x9d refers to that the side surface thereof is a surface inclined relative to the axis center direction of the coating roller and the diameter direction of the coating roller.
According to this configuration, by scraping off the excess portion of the paste supplied to the perimeter of the coating roller with the paste layer formation member, a paste layer having a desired thickness can be formed in the condition of being stable with respect to the shape on the taper-shaped circular convex thread of the coating roller, and by moving the target for coating in order to immerse in the paste layer on the taper portion of the circular convex thread of the coating roller, the paste can be transferred and applied to the target for coating. Even when the position of the target for coating held by the head somewhat deviates in the horizontal direction, and the target for coating is brought into contact with one of the pair of circular convex threads, the holding attitude of the head is adjusted while the position is kept regulated due to the contact and, therefore, application of the paste to the target for coating can be performed while deviation, etc., are controlled.
Preferably, the paste application apparatus is provided with a roller to be supplied with a paste on the perimeter surface and a transport mechanism which transports the target for coating to the required position above the roller, wherein a paste holding portion in which at least a part of the target for coating can enters and which can holds the paste is arranged on the perimeter surface of the aforementioned roller.
According to this configuration, since the paste is held in the paste holding portion on the perimeter surface of the roller, and a part of the target for coating, that is, the portion on the side of paste application, enters in this paste, the target for coating is immersed deeply in the paste and, therefore, large quantities of paste is applied to the target for coating.
In the aforementioned configuration, the paste holding portion is a circumferential groove arranged along the circumference on the perimeter surface of the roller, and the size of the circumferential groove is set in order that the portion on the side of paste application of the target for coating can enter with clearance. In this circumferential groove, the paste is held with a large thickness. In this case, since the contact area of the circumferential groove and the paste is large with respect to the quantity of the paste, flying of the paste is prevented.
In addition to this, examples of paste holding portions include a flexible holding layer for a paste which is formed from a flexible member on the perimeter surface of the roller and which has a paste holding gap inside thereof.
The target for coating is pressed against this flexible holding layer during application of the paste. The flexible holding layer deforms in such a manner as to avoid the target for coating. At this time, the paste contained in the paste holding gap inside the flexible holding layer flows towards the target for coating side and adheres to the target for coating.
More specifically, the aforementioned flexible holding layer is composed of numbers of pliable linear bodies arranged by implantation on the perimeter surface of the roller, numbers of elastic protrusions protruding from the perimeter surface of the roller in all directions, or an elastic body having numbers of gaps open toward the outer diameter side.
Regarding these flexible holding layers, the thickness of the paste is ensured within the range in which the flexible holding layer can be deformed by compression toward the perimeter surface of the roller side, and since the contact area with the paste is large, flying of the paste is prevented.
Preferably, the paste application apparatus is provided with a roller to be supplied with a paste on the perimeter surface, an application position setting mechanism for immersing at least a part of the target for coating in the paste on the perimeter surface of this roller at a required depth, and a scraping member for scraping the paste off the perimeter surface of the roller, wherein the aforementioned scraping member scrapes off the paste with a scraping depth larger than the immersion depth of the target for coating being immersed in the adhered paste while the scraping member is in non-contact with the perimeter surface of the roller.
The aforementioned target for coating is not limited to an electronic component, and may be any material as long as the paste is applied to the surface thereof.
The aforementioned roller may be any member which has a rotary surface and which has a function of being adhered with a paste on the rotary surface, and the shape of the perimeter surface thereof is not limited to the shape of a cylinder or the like.
The aforementioned paste is not restricted by the name, and any coating material having a viscosity required for application to a target for coating is used. For example, adhesives, conductive adhesives, flux, and any other coating material may be used.
According to the aforementioned configuration, the target for coating is immersed in the paste adhered on the perimeter surface of the roller, and a part of the paste is applied to the target for coating. Although the surface layer portion of the paste is exposed to the external air, and the target for coating is immersed therein, after coating is completed, the surface layer portion is scraped off with the scraping member, is mixed with, for example, other paste stored in the paste supply portion, and agitation is performed. According to this, the paste at the application position becomes always fresh, viscosity change due to drying of the paste is suppressed and, therefore, the quantity of the paste applied to the target for coating is stabilized.
Among the paste adhered on the perimeter surface of the roller, the inner layer portion which is not scraped off with the scraping member is not replaced with an adequately fresh paste. However, that portion does not involve in application of the paste to the target for coating, no effect is exerted on the quantity of the paste applied to the target for coating.
The surface layer portion of the adhered paste, which has been scraped off with the scraping member, may be taken out to the outside. However, when at least the tip portion of the scraping member is arranged above the aforementioned paste supply portion in order that the paste scraped by the scraping member flows into the paste supply portion under its own weight, the scraped paste and remaining past are mixed in the paste supply portion and, therefore, the total paste is self-agitated. According to this, viscosity change of the total paste is suppressed and, therefore, the quantity of the paste applied to the target for coating is stabilized. Since the scraped paste is returned to the paste supply portion, the quantity of decrease of the paste can be controlled to be minimum and, therefore, the paste can be used continuously for a long time.
In this case, since the scraping member is not brought into contact with the roller, wear does not occur, and degradation of the quality of the paste due to powders resulting from wear does not occur. The frictional heat between the scraping member and the roller does not occur and, therefore, degradation and cure of the paste due to the frictional heat between the two do not occur. Furthermore, since the scraping member does not wear, adjustment of the interval to the roller is unnecessary, and frequency of exchange of the scraping member itself is reduced.
Among the aforementioned configuration, the scraping member is not necessarily a plate in the shape of a squeegee having a sharp tip, a member having some thickness can be used, and the shape thereof is not limited to those shown in drawings in the embodiments.
The paste supply portion may be a paste bath including an open upper portion and the roller is arranged inside the open portion, and the paste supply portion may be formed from the liquid thickness adjustment member for adjusting the adhesion thickness of the paste on the perimeter surface of the roller and the perimeter surface of the roller. The liquid thickness adjustment member constituting the paste supply portion is arranged under the scraping member.
The aforementioned liquid thickness adjustment member is not necessarily a plate in the shape of a squeegee, a roller capable of rotating can also be used, and the shape thereof is not limited to those shown in drawings in the embodiments.
In the apparatus including the liquid thickness adjustment member arranged under the scraping member, when shifting members for shifting the paste toward the liquid thickness adjustment member side are arranged on both sides of the liquid thickness adjustment member in the shape surrounding the aforementioned scraping member from both sides, walls are thereby arranged on both sides of the paste supply portion and, therefore, this paste supply portion can store large quantities of paste. Furthermore, since the paste having been scraped with the scraping member can be stored in the paste supply portion and be used again, the paste can be used efficiently.
The paste application apparatus of the present invention may be provided with a paste supply portion for supplying the paste to the perimeter surface of the roller as a part of the apparatus, and this may be prepared independently of the apparatus. The application position setting mechanism may transport the target for coating in the horizontal direction relative to the perimeter surface of the roller, or may transport in the vertical direction.
Preferably, the paste application apparatus is provided with a roller having a rim-shaped perimeter, a paste supply mechanism for supplying the paste on the perimeter of the aforementioned roller so as to form the paste layer, and an application position setting mechanism for setting relative positions of the aforementioned roller and the aforementioned target for coating in order that the paste layer on the roller and the target for coating are brought into contact with each other and the paste is adhered to the surface of the aforementioned target for coating, wherein the aforementioned roller is provided with a blast plate which generates an air current by the rotation of the roller.